nerve

nerve

[nerv]

a macroscopic cordlike structure of the body, comprising a collection of nerve fibers that convey impulses between a part of the central nervous system and some other body region. See Appendix 2-6 and see color plates.

Depending on their function, nerves are known as sensory, motor, or mixed. Sensory nerves, sometimes called afferent nerves, carry information from the outside world, such as sensations of heat, cold, and pain, to the brain and spinal cord. Motor nerves, or efferent nerves, transmit impulses from the brain and spinal cord to the muscles. Mixed nerves are composed of both motor and sensory fibers, and transmit messages in both directions at once.

Together, the nerves make up the peripheral nervous system, as distinguished from the central nervous system (brain and spinal cord). There are 12 pairs of cranial nerves, which carry messages to and from the brain. Spinal nerves arise from the spinal cord and pass out between the vertebrae; there are 31 pairs, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. The various nerve fibers and cells that make up the autonomic nervous system innervate the glands, heart, blood vessels, and involuntary muscles of the internal organs.

Details of structure of components of nerve tissue.

accelerator n's the cardiac sympathetic nerves, which, when stimulated, accelerate the action of the heart.

spinal n's the 31 pairs of nerves arising from the spinal cord and passing out through the vertebrae; there are eight cervical, twelve thoracic, five lumbar, five sacral, and one coccygeal. , and see anatomic Table of Nerves in the Appendices.

Spinal nerves emerging from the spinal cord through the intervertebral foramina with muscles or muscle movements listed for specific levels. From McQuillan et al., 2002.

splanchnic n's those of the blood vessels and viscera, especially the visceral branches of the thoracic, abdominal (lumbar), and pelvic parts of the sympathetic trunks. See Appendix 3-5.

nerve

(nerv), [TA]

A whitish cordlike structure composed of one or more bundles (fascicles) of myelinated or unmyelinated nerve fibers, or more often mixtures of both, coursing outside the central nervous system, together with connective tissue within the fascicle and around the neurolemma of individual nerve fibers (endoneurium), around each fascicle (perineurium), and around the entire nerve and its nourishing blood vessels (epineurium), by which stimuli are transmitted from the central nervous system to a part of the body or the reverse. Nerve branches are given in the definition of the major nerve; many are also listed and defined under branch.

accessory nerve eleventh cranial nerve; origin, by cranial roots from the side of the medulla oblongata, and by spinal roots from the side of the spinal cord (from the upper three or more cervical segments); the roots unite to form the trunk of the accessory nerve, which divides into an internal branch (cranial portion) and an external branch (spinal portion); distribution, the internal branch to the vagus and thereby to the palate, pharynx, larynx, and thoracic viscera; the external branch branches to the sternocleidomastoid and trapezius muscles; modality, parasympathetic and motor.

acoustic nerve vestibulocochlear n.

afferent nerve any nerve that transmits impulses from the periphery toward the central nervous system; see sensory n.

alveolar nerves, superior the superior alveolar branches (anterior, middle, and posterior) that arise from the maxillary and infraorbital nerves, innervating the teeth of the upper jaw and the maxillary sinus, and forming the superior dental plexus.

ampullar nerve, anterior the branch of the vestibular nerve that innervates the ampulla of the anterior semicircular duct, ending around the hair cells of the ampullary crest.

ampullar nerve, inferior posterior ampullar n.

ampullar nerve, lateral the branch of the vestibular nerve that innervates the ampulla of the lateral semicircular duct, ending around the hair cells of the ampullary crest.

ampullar nerve, posterior the branch of the vestibular nerve that innervates the ampulla of the posterior semicircular duct, ending around the hair cells of the ampullary crest.

buccal nerveorigin, mandibular nerve; distribution, skin and mucous membrane of cheeks, gums, and perhaps the first two molars and the premolars; modality, general sensory.

cardiac nerve, inferior inferior cervical cardiac n.

cardiac nerve, middle middle cervical cardiac n.

cardiac nerve, superior superior cervical cardiac n.

cardiac nerves, thoracic branches of the second through fourth or fifth thoracic ganglia of the sympathetic trunk, supplying the heart and having a sympathetic (accelerator) modality as well as a visceral afferent one (chiefly for pain).

caroticotympanic nervesorigin, internal carotid plexus; inferior and superior nerves can be distinguished; together with tympanic nerve, they form the tympanic plexus; distribution, tympanic region and parotid gland; modality, sympathetic.

cervical nerves the eight pairs of nerves (C1–C8) that arise from the cervical segments of the spinal cord and, except for the last pair, leave the vertebral column above the correspondingly numbered vertebra. The ventral branches of the upper four, on either side, unite to form the cervical plexus, and those of the lower four, together with the ventral branch of the first thoracic nerve, form most of the brachial plexus.

cluneal nerves, inferior general sensory nerve branches of the posterior femoral cutaneous nerve, innervating the skin of the lower part of the buttocks.

cluneal nerves, middle general sensory nerve branches of the plexus formed by the lateral branches of dorsal branches of the first four sacral nerves, innervating ligaments of the sacrum and the skin over the posterior buttocks.

cluneal nerves, superior general sensory nerve branches of the dorsal branches of the upper lumbar nerves, innervating the skin of the upper part of the buttocks.

coccygeal nerve either of the thirty-first pair of spinal nerves (Co), arising from the coccygeal segment of the spinal cord.

cochlear nerve the part of the vestibulocochlear nerve concerned with hearing, consisting of fibers that arise from the bipolar cells in the spiral ganglion and have their receptors in the spiral organ of the cochlea.

cutaneous nerve, perforating one of the inferior cluneal nerves which pierces the sacrotuberous ligament and supplies the skin over the inferomedial gluteus maximus; it is absent in one third of the population.

cutaneous nerve of calf, lateralorigin, common fibular nerve; distribution, skin of lateral side of back of leg, rarely may continue as the sural nerve; modality, general sensory.

cutaneous nerve of calf, medialorigin, tibial nerve; usually joins fibular communicating branch of common fibular nerve to form the sural nerve; distribution, may continue as the sural nerve; modality, general sensory.

cutaneous nerve of foot, intermediate dorsalorigin, superficial fibular nerve; branches, dorsal digital nerves of foot; distribution, skin of front of lower third of leg and dorsum of foot, and skin and joints of adjacent sides of third and fourth, and of fourth and fifth toes; modality, general sensory.

cutaneous nerve of foot, lateral dorsalorigin, continuation of sural nerve; distribution, skin and joints of lateral side of foot and fifth toe; modality, general sensory.

cutaneous nerve of foot, medial dorsalorigin, superficial fibular nerve; distribution, skin and joints of medial side of foot and big toe, and adjacent sides of second and third toes; modality, general sensory.

cutaneous nerve of forearm, lateralorigin, continuation of musculocutaneous nerve; distribution, skin over radial side of forearm and sometimes an area of skin of dorsum of hand; modality, general sensory.

1. nerves supplying the third, fourth, and fifth toes; origin, intermediate dorsal cutaneous nerve; distribution, skin and joints of adjacent sides of third and fourth, and of fourth and fifth toes; modality, general sensory.

2. nerves supplying the first and second toes; origin, medial terminal division of deep fibular nerve; distribution, skin and joints of adjacent sides of great and second toes; modality, general sensory.

digital nerves of lateral plantar nerve, common plantarnumber, two; origin, superficial branch of lateral plantar nerve; branches, the medial nerve gives rise to two proper plantar digital nerves; distribution, the lateral one to the short flexor muscle of little toe and to skin and joints of lateral side of sole and little toe; the medial one to adjacent sides of fourth and fifth toes; modality, motor and general sensory.

digital nerves of lateral plantar nerve, proper plantarorigin, common plantar digital nerves; distribution, short flexor muscle of little toe, skin and joints of lateral side of sole and little toe, and adjacent sides of fourth and fifth toes; modality, motor and general sensory.

digital nerves of medial plantar nerve, common plantarnumber, four; origin, medial plantar nerve; branches, muscular and proper plantar digital nerves; distribution, flexor hallucis brevis muscle and first lumbrical muscles, skin and joints of medial side of foot and big toe, and adjacent sides of first and second, second and third, and third and fourth toes; modality, motor and general sensory.

digital nerves of medial plantar nerve, proper plantarorigin, common plantar digital nerves; distribution, skin and joints of medial side of first toe, and adjacent sides of first and second, second and third, and third and fourth toes; the nerves extend to the dorsum to supply nail beds and tips of toes; modality, general sensory.

digital nerves of median nerve, proper palmarorigin, common palmar digital nerves; distribution, first two lumbrical muscles, skin and joints of both sides and palmar aspect of thumb, index, and middle fingers, radial side of ring finger, and back of distal aspect of these digits; modality, general sensory and motor.

digital nerves of radial nerve, dorsalorigin, superficial branch of radial nerve; distribution, skin and joints of back of thumb, index finger, and part of middle finger, as far distally as the distal phalanx; modality, general sensory.

digital nerves of ulnar nerve, dorsalorigin, dorsal branch of ulnar nerve; distribution, skin and joints of medial side of little finger, dorsal aspects of adjacent sides of little and ring fingers and of ring and middle fingers; modality, general sensory.

digital nerves of ulnar nerve, proper palmar proper palmar digital nerves of ulnar nerve: origin, the lateral of the two common palmar digital nerves from the superficial branch of the ulnar nerve; distribution, skin and joints of adjacent sides of fourth and fifth fingers; modality, general sensory.

fibular nerve, commonorigin, sciatic nerve in lower part of thigh; branches and distribution, supplies short head of biceps femoris muscle (while still incorporated in sciatic nerve), gives off lateral sural cutaneous nerve and fibular communicating branch as it descends in popliteal fossa, supplies knee and superior tibiofibular joints and tibialis anterior muscle, and divides into superficial and deep fibular nerves; modality, general sensory and motor.

fibular nerve, deeporigin, a terminal branch of common fibular nerve; branches and distribution, winds around the neck of the fibula and descends on the interosseous membrane to the front of the ankle; gives off muscular branches to anterior tibial, extensor of great toe, long extensor of toes, and third fibular muscles, and a twig to ankle joint; a lateral terminal division supplies the short extensor muscle of toes and tarsal joints; medial terminal division, or digital branch, divides into dorsal digital nerves for skin and joints of adjacent sides of first and second toes; modality, general sensory and motor.

fibular nerve, superficialorigin, a terminal branch of common fibular nerve; branches and distribution, descends in front of the fibula, supplies long and short fibular muscles and, in the lower part of the leg, divides into the muscular branches, medial and intermediate dorsal cutaneous nerves; modality, general sensory and motor.

frontal nerveorigin, ophthalmic division of trigeminal nerve; enters the orbit through the superior orbital fissure; branches, supraorbital and supratrochlear nerves; distribution, chiefly to the forehead and scalp; modality, general sensory.

furcal nerve the fourth lumbar nerve.

fusimotor nerves those with nerve endings that innervate intrafusal fibers of the muscle spindle.

gangliated nerve any nerve of the sympathetic nervous system.

genitofemoral nerveorigin, lumbar plexus (L1–L2); branches, genital and femoral branches; distribution, cremaster muscle, skin of scrotum or labium majus and of adjacent area of thigh and femoral triangle; modality, general sensory and motor.

glossopharyngeal nerve ninth cranial nerve; origin, several rootlets from lateral side of upper part of medulla oblongata, between the olive and the inferior cerebellar peduncle; branches, tympanic nerve, pharyngeal, stylopharyngeal, tonsillar, and lingual branches, branch to the carotid sinus, and a branch communicating with the auricular branch of the vagus nerve; distribution, it has two enlargements (superior and inferior ganglia) and supplies the tongue, pharynx, and parotid gland; modality, motor, parasympathetic, and general, special, and visceral sensory.

gustatory nerves sensory nerve fibers innervating the taste buds and associated with taste, including branches from the lingual and glossopharyngeal nerves.

hemorrhoidal nerves, inferior

1. nervi anales inferiores.

2. inferior anal n's.

hypoglossal nerve twelfth cranial nerve; origin, several rootlets in the anterolateral sulcus between the olive and the pyramid of the medulla oblongata; it passes through the hypoglossal canal to the tongue; branches, lingual branches; distribution, styloglossus, hyoglossus, and genioglossus muscles and intrinsic muscles of the tongue; modality, motor.

iliohypogastric nerveorigin, lumbar plexus—L1 (sometimes T12); branches, lateral and anterior cutaneous branches; distribution, the skin above the pubis and over the lateral side of the buttock, and occasionally the pyramidal muscle; modality, motor and general sensory.

inhibitory nerve one that transmits impulses resulting in a decrease in functional activity.

intercostobrachial nerves two nerves arising from the intercostal nerves and supplying the skin of the upper limb. The first is constant: origin, second intercostal nerve; distribution, skin on back and medial aspect of arm; modality, general sensory. A second intercostobrachial nerve is often present;origin, third intercostal nerve; distribution, skin of axilla and medial aspect of arm; modality, general sensory.

intermediate nerve the smaller root of the facial nerve, lying between the main root and the vestibulocochlear nerve; it joins the main root at, or merges with, the geniculate ganglion at the geniculum of the facial nerve; branches, chorda tympani and greater petrosal nerve; distribution, lacrimal, nasal, palatine, submandibular, and sublingual glands, and anterior two-thirds of tongue; modality, parasympathetic and special sensory.

interosseous nerve of forearm, posteriororigin, continuation of deep branch of radial nerve; distribution, long abductor muscle of thumb, extensor muscles of the thumb and second finger, and wrist and intercarpal joints; modality, motor and general sensory.

laryngeal nerve, external the smaller of the two branches into which the superior laryngeal nerve divides, descending under cover of the sternothyroid muscle and innervating the cricothyroid and the inferior constrictor of the pharynx; modality, motor.

lingual nerveorigin, mandibular nerve, descending to the tongue, first medial to the mandible and then under cover of the mucous membrane of the mouth; branches, sublingual nerve, lingual branch, branch to the isthmus of the fauces, and branches communicating with the hypoglossal nerve and chorda tympani; distribution, anterior two-thirds of tongue, adjacent areas of mouth, gums, isthmus of fauces; modality, general sensory.

lumbar nerves the five pairs of nerves (L1–L5) that arise from the lumbar segments of the spinal cord, each pair leaving the vertebral column below the correspondingly numbered vertebra. The ventral branches of these nerves participate in the formation of the lumbosacral plexus.

median nerveorigin, lateral and medial cords of brachial plexus—C6–T1; branches, anterior interosseous nerve of forearm, common palmar digital nerves, and muscular and palmar branches, and a communicating branch with the ulnar nerve; distribution, ultimately, skin on front of lateral part of hand, most of flexor muscles of front of forearm, most of short muscles of thumb and elbow joint, and many joints of hand; modality, general sensory.

occipital nerve, greaterorigin, medial branch of dorsal branch of C2; distribution, semispinal muscle of head and skin of scalp as far forward as the vertex; modality, general sensory and motor.

occipital nerve, lesserorigin, superficial cervical plexus (C2–C3); distribution, ascends behind the auricle and supplies some of the skin on the side of the head and on the cranial surface of the auricle; modality, general sensory.

occipital nerve, thirdorigin, medial branch of dorsal branch of C3; distribution, skin of upper part of back of neck and head; modality, general sensory.

optic nerve second cranial nerve, the so-called nerve of sight, actually part of the central nervous system throughout its course; it consists chiefly of axons and central processes of cells of the ganglionic layer of the retina, which leave the orbit through the optic canal, and joins with its opposite number to form the optic chiasm (the medial fibers of each nerve crossing over to the opposite side), then continues as the optic tract to end in the lateral geniculate body.

pharyngeal nerve a nerve running from the posterior part of the pterygopalatine ganglion, through the pharyngeal canal with the pharyngeal branch of the maxillary artery, to the mucous membrane of the nasal part of the pharynx posterior to the auditory tube.

phrenic nerves, accessory an inconstant contribution of the fifth cervical nerve to the phrenic nerve; when present, they run a separate course to the root of the neck or into the thorax before joining the phrenic nerve.

plantar nerve, lateralorigin, the smaller of terminal branches of tibial nerve; branches, muscular, superficial, and deep branches; distribution, lying between first and second layers of muscles of sole, it supplies the quadratus of sole, abductor of little toe, short flexor of little toe, adductor of great toe, interosseous, and second, third, and fourth lumbrical muscles, and gives off cutaneous and articular twigs to lateral side of sole and fourth and fifth toes; modality, general sensory and motor.

plantar nerve, medialorigin, the larger of the terminal branches of tibial nerve; branches, common plantar digital nerves and muscular branches; distribution, abductor of great toe, short flexor of toes, short flexor of great toe, and first lumbrical muscles, and cutaneous and articular twigs to the medial side of the sole, and to the first to fourth toes; modality, general sensory and motor.

radial nerveorigin, posterior cord of brachial plexus (C6–C8, and sometimes C5 and T1); branches, posterior cutaneous and inferior lateral cutaneous nerves of arm, posterior cutaneous nerve of forearm, muscular, deep, and superficial branches; distribution, descending in the back of arm and forearm, it is ultimately distributed to skin on back of arm, forearm, and hand, extensor muscles on back of arm and forearm, and elbow joint and many joints of hand; modality, general sensory and motor.

rectal nerves, inferior inferior anal n's.

recurrent nerve

1. nervus laryngeus recurrens.

2. recurrent laryngeal n.

saccular nerve the branch of the vestibular nerve that innervates the macula of the saccule.

sacral nerves (S1–S5) that arise from the sacral segments of the spinal cord; the ventral branches of the first four pairs participate in the formation of the sacral plexus.

saphenous nerveorigin, termination of femoral nerve, descending first with femoral vessels and then on medial side of leg and foot; branches, infrapatellar and medial crural cutaneous branches; distribution, knee joint, subsartorial and patellar plexuses, skin on medial side of leg and foot; modality, general sensory.

sciatic nerve the largest nerve of the body: origin, sacral plexus (L4–S3); it leaves the pelvis through the greater sciatic foramen; branches, divides into the tibial and common fibular nerves, usually in lower third of thigh; distribution, see individual nerve branches; modality, general sensory and motor.

spinal nerves the thirty-one pairs of nerves that arise from the spinal cord and pass out between the vertebrae, including the eight pairs of cervical, twelve of thoracic, five of lumbar, five of sacral, and one pair of coccygeal nerves.

splanchnic nerves those of the blood vessels and viscera, especially the visceral branches of the thoracic, lumbar, and pelvic parts of the sympathetic trunks.

splanchnic nerve, greaterorigin, thoracic sympathetic trunk and fifth through tenth thoracic ganglia; distribution, descending through the diaphragm or its aortic openings, ends in celiac ganglia and plexuses, with a splanchnic ganglion commonly occurring near the diaphragm; modality, preganglionic sympathetic and visceral afferent.

subcostal nerveorigin, anterior branch of twelfth thoracic nerve; distribution, skin of lower abdomen and lateral side of gluteal region, parts of abdominal transverse, oblique, and rectus muscles, and usually the pyramidal muscle, and adjacent peritoneum; modality, general sensory and motor.

subscapular nervesorigin, posterior cord of brachial plexus (C5); distribution, usually two or more nerves, upper and lower, supplying subscapular and teres major muscles; modality, motor.

supraclavicular nerves a term denoting collectively the common trunk, which is a branch of the cervical plexus (C3–C4) and which emerges under cover of the posterior border of the sternocleidomastoid muscle and divides into the intermediate, lateral, and medial supraclavicular nerves.

supratrochlear nerveorigin, frontal nerve, from ophthalmic nerve; distribution, leaves orbit at medial end of supraorbital margin and supplies the forehead and upper eyelid; modality, general sensory.

sural nerveorigin, medial sural cutaneous nerve and fibular communicating branch of common fibular nerve; branches, lateral dorsal cutaneous nerve and lateral calcaneal branches; distribution, skin on back of leg, and skin and joints on lateral side of heel and foot; modality, general sensory.

tentorial nerve a branch that arises from the ophthalmic nerve close to its origin from the trigeminal ganglion, turning back to innervate the dura mater of the tentorium cerebelli and falx cerebri; modality, general sensory.

thoracic nerves the twelve pairs of spinal nerves (T1–T12) that arise from the thoracic segments of the spinal cord, each pair leaving the vertebral column below the correspondingly numbered vertebra. They innervate the body wall of the thorax and upper abdomen.

tibial nerve tibial nerve: origin, sciatic nerve in lower part of thigh; branches, interosseous nerve of leg, medial cutaneous nerve of calf, sural nerve, and medial and lateral plantar nerves, and muscular and medial calcaneal branches; distribution, while still incorporated in the sciatic nerve, it supplies the semimembranous and semitendinous muscles, long head of biceps, and great adductor muscle; it supplies the knee joint as it descends in the popliteal fossa and, continuing into the leg, supplies the muscles and skin of the calf and sole of the foot, and the toes; modality, general sensory and motor.

trigeminal nerve fifth cranial nerve, which emerges from the lateral surface of the pons as a motor and a sensory root, together with some intermediate fibers. The sensory root expands into the trigeminal ganglion, which contains the cells of origin of most of the sensory fibers, and from which the three divisions of the nerve arise. See mandibular n., maxillary n., and ophthalmic n. The trigeminal nerve is sensory in supplying the face, teeth, mouth, and nasal cavity, and motor in supplying the muscles of mastication.

trochlear nerve fourth cranial nerve; origin, the fibers of each trochlear nerve (one on either side) decussate across the median plane and emerge from the back of the brain stem below the corresponding inferior colliculus; distribution, runs forward in lateral wall of cavernous sinus, traverses the superior orbital fissure, and supplies superior oblique muscle of eyeball; modality, motor.

ulnar nerveorigin, medial and lateral cords of brachial plexus (C7–T1); branches, muscular, dorsal, palmar, superficial, and deep branches; distribution, ultimately to skin on front and back of medial part of hand, some flexor muscles on front of forearm, many short muscles of hand, elbow joint, many joints of hand; modality, general sensory and motor.

unmyelinated nerve one whose axons are not encased in a myelin sheath.

utricular nerve the branch of the vestibular nerve that innervates the macula of the utricle.

utriculoampullary nerve a nerve that arises by peripheral division of the vestibular nerve, and supplies the utricle and ampullae of the semicircular ducts.

vagus nerve vagus nerve: tenth cranial nerve; origin, by numerous rootlets from lateral side of medulla oblongata in the groove between the olive and the inferior cerebellar peduncle; branches, superior and recurrent laryngeal nerves, meningeal, auricular, pharyngeal, cardiac, bronchial, gastric, hepatic, celiac, and renal branches, pharyngeal, pulmonary, and esophageal plexuses, and anterior and posterior trunks; distribution, descending through the jugular foramen, it presents as a superior and an inferior ganglion, and continues through the neck and thorax into the abdomen. It supplies sensory fibers to the ear, tongue, pharynx, and larynx, motor fibers to the pharynx, larynx, and esophagus, and parasympathetic and visceral afferent fibers to thoracic and abdominal viscera; modality, parasympathetic, visceral afferent, motor, general sensory.

vasoconstrictor nerve one whose stimulation contracts blood vessels.

vasodilator nerve one whose stimulation dilates blood vessels.

vasomotor nerve one concerned in controlling the caliber of vessels, whether as a vasoconstrictor or vasodilator.

vestibular nerve the posterior part of the vestibulocochlear nerve, which is concerned with the sense of equilibrium. It consists of fibers arising from bipolar cells in the vestibular ganglion, and divides peripherally into a rostral and a caudal part, with receptors in the ampullae of the semicircular canals, the utricle, and the saccule.

vestibulocochlear nerve eighth cranial nerve; it emerges from the brain between the pons and the medulla oblongata, at the cerebellopontine angle and behind the facial nerve. It divides near the lateral end of the internal acoustic meatus into two functionally distinct and incompletely united components, the vestibular nerve and the cochlear nerve, and is connected with the brain by corresponding roots, the vestibular and the cochlear roots.

vidian nerve n. of pterygoid canal.

vidian nerve, deep deep petrosal n.

zygomatic nerveorigin, maxillary nerve, entering the orbit through the inferior orbital fissure; branches, zygomaticofacial and zygomaticotemporal branches; distribution, communicates with the lacrimal nerve and supplies the skin of the temple and adjacent part of the face; modality, general sensory.

nerve

(nûrv)

n.

1. Any of the cordlike bundles of fibers made up of neurons through which sensory stimuli and motor impulses pass between the brain or other parts of the central nervous system and the eyes, glands, muscles, and other parts of the body. Nerves form a network of pathways for conducting information throughout the body.

2. The sensitive tissue in the pulp of a tooth.

3. nerves Nervous agitation caused by fear, anxiety, or stress: had a sudden attack of nerves.

4. A vein or rib in the wing of an insect.

nerve

[nurv]

Etymology: L, nervus

one or more bundles of impulse-carrying fibers, myelinated or unmyelinated or both, that connect the brain and the spinal cord with other parts of the body. Nerves transmit afferent impulses from receptor organs toward the brain and spinal cord and efferent impulses peripherally to the effector organs. Each nerve consists of an epineurium enclosing fasciculi of nerve fibers; each fasciculus is surrounded by its own sheath of connective tissue, or epineurium. Individual nerve fibers, which are microscopic, consist of formed elements within a matrix of protoplasm enclosed in endoneurium that are enclosed in a neurilemmal sheath. Inside the neurilemma are nerve fibers, also enclosed in a myelin sheath. See also axon, dendrite, neuroglia, neuron, Schwann cell.

Nerves of the spinal cord

nerve

Vox populi A popular adjective for cheekiness, brass, “balls,” as in she's got nerve. Cf Nerves.

nerve

(nĕrv) [TA]

A whitish cordlike structure composed of one or more bundles (fascicles) of myelinated or unmyelinated nerve fibers, or more often mixtures of both, coursing outside of the central nervous system, together with connective tissue within the fascicle and around the neurolemma of individual nerve fibers (endoneurium), around each fascicle (perineurium), and around the entire nerve and its nourishing blood vessels (epineurium), by which stimuli are transmitted from the central nervous system to a part of the body or the reverse. Synonym(s): nervus [TA] .

[L. nervus]

nerve

(nerv) [L. nervus, sinew]

NERVE STRUCTURE

Parallel axons running together inside a thick connective tissue sheath (an epineurium). In the nerve, axons are wrapped into small bundles by thin connective tissue sheaths (endoneuria); each small bundle of axons is called a fascicle. The neuronal cell bodies of a nerve's axons are in the brain, the spinal cord, or ganglia, but the nerves run only in the peripheral nervous system. Nerves with axons that conduct electrochemical impulses toward the CNS are afferent, nerves with axons that conduct impulses away from the CNS are efferent, and nerves with both afferent and efferent axons are mixed. Nerves in the peripheral nervous system are roughly analogous to tracts in the CNS and, like tracts, act as highways that axons can join or leave on the way from their origin to their target. See: ansa; cell; nervus.; illustration

Tests for Loss of Function

The assessment of nerve injury includes a careful neurological examination, sometimes accompanied by tests, e.g., electromyography or nerve conduction studies.

abducens nerve

A somatic motor nerve originating in the abducens nucleus in the pons. It runs in the subarachnoid space and the cavernous sinus inside the skull, enters the back of the orbit through the superior orbital fissure, and innervates the lateral rectus muscle.

adrenergic nerve

afferent nerve

alveolar nerve

Any of the sensory nerves to the teeth; they are branches of the trigeminal nerve (CN V). The superior alveolar nerves innervate the upper teeth and gingivae; the inferior alveolar nerves innervate the lower teeth and gingivae. The anterior superior alveolar nerves, branches of the infraorbital nerve (from CN V2), run in canals in the anterior wall of the maxillary sinus and innervate the upper incisors, canines, premolars, and often part of the first molar. Sometimes there is a middle superior alveolar nerve that innervates the premolars and first molar. The posterior superior alveolar nerves (also from CN V2) innervate the rest of the upper molars. The inferior alveolar nerve (from CN V3) runs in the mandibular canal, giving off branches to the lower teeth and gingivae as it passes.

Synonym: dental nerve

antebrachial cutaneous nerve

auditory nerve

The component of the vestibulocochlear nerve (CN VIII) that carries axons conveying sound information between the spiral ganglion in the inner ear and the cochlear nuclei in the brainstem. Synonym: acoustic nerve; cochlear nerve

auricular nerve

Any of three nerves, the great auricular nerve, the posterior auricular nerve, or the auricular branch of the vagus nerve (CN X). The great auricular nerve is a sensory branch of the cervical plexus composed of axons from spinal cord segments C2–C3; it innervates the skin and fascia behind the ear, on the lower part of the pinna of the ear, and over the angle of the jaw. The posterior auricular nerve is a motor branch of the facial nerve (CN VII) that innervates the posterior and intrinsic auricular muscles. The auricular branch of the vagus nerve is a sensory nerve emerging from the superior ganglion of the vagus nerve, joined by branches from the glossopharyngeal (CN IX) and facial nerves, and innervating the lower part of the tympanic membrane and the floor of the external auditory canal.

auriculotemporal nerve

A sensory branch of the mandibular nerve (CN V3) It passes through the parotid gland en route to the ear, where it innervates skin of the pinna, external auditory canal, and tympanic membrane.

brachial cutaneous nerve

buccal nerve

Sensory

It innervates skin over the lower cheek, mucous membranes inside the cheek, and the buccal gingivae along the second and third lower molar.

Motor

It innervates the lateral pterygoid muscle.

2. A motor branch of the facial nerve (CN VII) that innervates the buccinator and neighboring facial muscles.

calcaneal nerve

Any of the nerves that are sensory branches of the tibial nerve and innervate the skin on the heel and the medial side of the sole of the foot.

cardiac nerve

Any of the autonomic nerves traveling to the cardiac plexus. The three main sympathetic nerves (superior cardiac nerve, middle cardiac nerve, and inferior cardiac nerve) originate in the superior, middle, and inferior cervical sympathetic ganglia. The preganglionic parasympathetic innervation of the cardiac plexus is from the vagus nerve (CN X).

carotid nerve

1. Any of the nerves from the superior cervical ganglion of the sympathetic trunk that form plexuses around the carotid arteries. The internal carotid nerves form a plexus around the internal carotid artery inside the carotid canal; the external carotid nerves form a plexus around the external carotid artery.

2. Carotid sinus nerve.

carotid sinus nerve

A sensory branch of the glossopharyngeal nerve (CN IX) carrying signals from the baroceptors (blood pressure receptors) in the bifurcation of the carotid artery to the nucleus of the solitary tract (nucleus solitarius).

cervical nerve

1. Any of the eight pairs of spinal nerves that originate in the cervical segments of the spinal cord. They are abbreviated C1 to C8. The first cervical spinal nerve (C1) emerges from the spinal canal above the first cervical vertebra; the eighth cervical spinal nerve (C8) emerges from between the seventh cervical vertebra and the first thoracic vertebra. Cervical spinal nerves innervate the neck, shoulders, and arms.

2. A motor branch of the facial nerve (CN VII) that emerges from the lower end of the parotid gland and runs down behind the angle of the jaw to innervate the platysmus muscle.

cholinergic nerve

A nerve that uses acetylcholine as its main neurotransmitter.

ciliary nerve

Either of two nerves, the long ciliary nerve and the short ciliary nerve, that carry sensory axons and postganglionic sympathetic fibers that innervate the ciliary body, iris, and cornea of the eye. The long ciliary nerves are branches of the nasociliary nerve; the short ciliary nerves come from the ciliary ganglion and also contain preganglionic parasympathetic axons.

coccygeal nerve

The tiny final nerve of the spinal cord, which is composed of axons from spinal nerves S4–S5; it innervates the coccygeus and levator ani muscles and the skin over the coccyx.

cochlear nerve

collateral nerve

common fibular nerve

common peroneal nerve

One of the two divisions of the sciatic nerve in the leg. The sciatic nerve branches into the tibial and common peroneal nerves in the apex of the popliteal fossa. The common peroneal nerve winds around the proximal neck of the fibula to reach the anterior leg where it divides into the superficial and deep peroneal nerves. The common peroneal nerve innervates the knee joint and the skin of the lateral side of the upper leg.

Synonym: common fibular nerve

CRANIAL NERVES AND THEIR DISTRIBUTIONS

cranial nerve

Abbreviation: CN

Any of the twelve pairs of nerves that leave the cranial cavity through foramina in the skull and innervate the head. The cranial nerves are numbered in the order they contact the brain; from anterior to posterior, they are the olfactory (CN I), optic (CN II), oculomotor (CN III), trochlear (CN IV), trigeminal (CN V), abducens (CN VI), facial (CN VII), vestibulocochlear (CN VIII), glossopharyngeal (CN IX), vagus (CN X), spinal accessory (CN XI), and hypoglossal (CN XII) nerves. The central nuclei for all the cranial nerves, except the olfactory nerve, are in the brainstem. See: illustration

Diagnosis

Lesions of the cranial nerves give rise to the following alteration(s): First (CN I; olfactory): Loss of the sense of smell. Second (CN II; optic): Blindness in all or part of a visual field. Third (CN III; oculomotor): Ptosis (drooping) of the eyelid, deviation of the eyeball outward, immobility of the pupil, double vision. Fourth (CN IV; trochlear): Rotation of the eyeball upward and outward, double vision. Fifth (CN V; trigeminal):

cutaneous nerve

deep fibular nerve

deep peroneal nerve

One of the two major branches of the common peroneal nerve formed as the latter winds around the proximal neck of the fibula. The deep peroneal nerve runs along the interosseous membrane (between the fibula and tibia) into the dorsal foot. It innervates anterior leg muscles and the skin of the dorsal surface of the foot.

Synonym: deep fibular nerve

deep petrosal nerve

A bundle of postganglionic sympathetic axons from the superior cervical ganglion. These axons take the internal carotid nerve into the carotid canal in the skull, where they form the internal carotid plexus. From this plexus, the axons emerge as the deep petrosal nerve, which then joins the greater petrosal nerve in the vidian canal, en route to the pterygopalatine ganglion.

eighth cranial nerve

eleventh cranial nerve

ethmoidal nerve

Either of two nerves, the anterior ethmoidal nerve or the posterior ethmoidal nerve, that are sensory branches of the nasociliary nerve.

excitatory nerve

A nerve that heightens, increases, or starts the activity of its target.

excitoreflex nerve

A visceral nerve whose stimulation causes reflex action.

SUPERFICIAL BRANCHES OF FACIAL NERVE (7TH CRANIAL))

facial nerve

A mixed nerve consisting of efferent fibers supplying the facial muscles, the platysma muscle, the submandibular and sublingual glands; and of afferent fibers from taste buds of the anterior two thirds of the tongue and from the muscles.

Sensory

Taste fibers from the anterior two thirds of the tongue and the soft palate follow the chorda tympani to their neuronal cell bodies in the geniculate ganglion; the axons of these neurons follow the nervus intermedius (the sensory root of the facial nerve) into the pons where they synapse in the nucleus of the tractus solitarius (the gustatory nucleus).

Motor

Somatic motor axons from the motor nucleus of the facial nerve in the pons emerge as the motor root of the facial nerve and enter the bone of the skull through the internal auditory meatus. The motor axons follow the facial canal inside the temporal bone and exit the skull through the stylomastoid foramen. From there, the axons innervate all the muscles of facial expression. Preganglionic parasympathetic axons from the superior salivatory nucleus take the nervus intermedius to the region of the geniculate ganglion inside the facial canal. From there, some of the axons join the chorda tympani and later reach the submandibular ganglion by following the lingual nerve. Other preganglionic parasympathetic axons follow the major superficial petrosal nerve and the vidian nerve to reach the pterygopalatine ganglion.

femoral nerve

1. A mixed nerve originating in the lumbar plexus and composed of axons from spinal cord segments L2–L4. It runs into the thigh, passing under the inguinal ligament, on the lateral side of the femoral vessels. It then divides into a number of branches, including the anterior cutaneous nerves of the thigh and the saphenous nerve.

Sensory

The femoral nerve and its branches innervate the skin along the distal anterior thigh, the front and medial side of the knee, and the medial leg and foot. They also innervate the hip and knee joints.

Motor

The femoral nerve and its branches innervate the pectineus, sartorius, and quadriceps muscles.

2. A sensory branch of the genitofemoral nerve that runs in the femoral sheath and innervates skin over the femoral triangle.

fifth cranial nerve

first cranial nerve

fourth cranial nerve

frontal nerve

A sensory branch of the ophthalmic nerve (CN V1). It runs in the orbit above the eye where it branches into the supraorbital and supratrochlear nerves. The frontal nerve innervates the conjunctiva lining the upper eyelid; the mucosa of the frontal sinus; and the skin of the upper eyelids, forehead, and front half of the scalp.

GABAergic nerve

A nerve that uses gamma-aminobutyric acid (GABA ) as its main neurotransmitter.

gangliated nerve

Any nerve of the sympathetic nervous system.

gastric nerve

Any of the autonomic nerves to the stomach from the esophageal plexus that are composed of axons from the vagus (CN X) and greater splanchnic nerves.

genital nerve

A sensory branch of the genitofemoral nerve that enters the inguinal canal through the internal ring and innervates the cremaster muscles and scrotal skin in males and the skin of the mons pubis and the labium majus in females.

genitofemoral nerve

A sensory nerve originating in the lumbar plexus and composed of axons from spinal cord segments L2–L3. It runs along the surface of the psoas major muscle where it divides into a genital branch and a femoral branch; the branches innervate the skin of the scrotum or labium and the skin over the femoral triangle.

GLOSSOPHARYNGEAL NERVE

glossopharyngeal nerve

A mixed nerve that is sensory for taste and for the carotid sinus and body, and motor for secretion of saliva and contraction of the pharynx.

Sensory

Taste fibers from the posterior third of the tongue join visceral sensory fibers from the pharynx, auditory tube, middle ear, carotid sinus, and carotid body and run back to their neuronal cell bodies in the superior and inferior ganglia of the glossopharyngeal nerve, located in the jugular foramen. The axons of these ganglionic neurons follow the glossopharyngeal roots into the hindbrain where they synapse in the nucleus of the tractus solitarius and the spinal nucleus of the trigeminal nerve.

Motor

The glossopharyngeal nerve emerges from the medulla as a line of small rootlets just anterior to the rootlets of the vagus nerve (CN X). The glossopharyngeal rootlets collect into a single nerve that emerges from the skull through the jugular foramen, along with the vagus and spinal accessory (CN XI) nerves. The glossopharyngeal nerve then divides into branches as it runs along the stylopharyngeus muscle.

Course

CN IX.

Synonym: ninth cranial nerve See: illustration

greater occipital nerve

A prominent sensory component of the dorsal ramus of spinal nerve C2. It leaves the spinal canal between the first and second vertebrae and runs up the back of the neck to innervate the skin over the occipital bone of the skull.

Synonym: occipital nerve

greater petrosal nerve

A sensory and autonomic branch of the facial nerve (CN VII) that carries taste axons from the palate and preganglionic parasympathetic axons destined for the pterygopalatine ganglion. The greater petrosal nerve leaves the facial nerve in the facial canal near the geniculate ganglion; it runs forward in the greater petrosal groove on the surface of the petrous portion of the temporal bone, enters the forward edge of the foramen lacerum, and merges with the deep petrosal nerve to form the vidian nerve.

greater superficial petrosal nerve

hepatic nerve

Any of the branches of the gastric nerves that supply autonomic innervation of the liver and biliary system.

hypoglossal nerve

A somatic motor nerve originating in the hypoglossal nucleus of the hindbrain. The nerve collects from a short line of rootlets and exits the skull through the hypoglossal canal. It then innervates the intrinsic muscles of the tongue (the superior and inferior longitudinal, transverse, and vertical muscles) and three of the extrinsic muscles of the tongue (the styloglossus, hyoglossus, and genioglossus muscles).

iliohypogastric nerve

A sensory nerve originating in the lumbar plexus and composed of axons from spinal cord segment L1. It runs parallel to the iliac crest and innervates the skin in a band from the upper lateral side of the buttock to the abdomen above the pubis.

ilioinguinal nerve

A sensory nerve originating in the lumbar plexus and composed of axons from spinal cord segment L1. It runs with the spermatic cord (in males) or the round ligament (in females) through the internal inguinal ring to the skin of the scrotum or labium majus. It innervates the skin of the proximal and medial thigh and of the scrotum or labium majus.

inferior gluteal nerve

A mixed nerve of axons from spinal nerves L5–S2. It follows the sciatic nerve out of the pelvis, and it innervates the gluteus maximus muscle.

inferior rectal nerve

A mixed nerve that is a branch of the pudendal nerve. It follows the inferior rectal vessels to innervate the external anal sphincter, the walls of the lower anal canal, and the perineal skin around the anus.

infraorbital nerve

The terminal branch of the maxillary nerve (CN V2). It is a sensory nerve that leaves the floor of the orbit through the infraorbital foramen and innervates the upper incisors and canine teeth, the mucosa of the maxillary sinus, and the skin of the lower eyelid, cheek, side of the nose, and upper lip.

infratrochlear nerve

A sensory branch of the nasociliary nerve. It runs along the medial wall of the orbit and innervates the skin and lining of the upper eyelid.

inhibitory nerve

A nerve that dampens, decreases, or stops the activity of its target.

intercostal nerve

Any of the eleven pairs of parallel nerves originating in the ventral rami of thoracic spinal nerves T1–T11. Each intercostal nerve runs forward, with a companion intercostal artery and vein, along the lower inner edge of its corresponding rib. It innervates the intercostal muscles and overlying skin.

lateral cutaneous nerve of the arm

lateral cutaneous nerve of the forearm

lateral femoral cutaneous nerve

A sensory nerve that originates from the lumbar plexus and is composed of axons from spinal cord segments L2–L3. It runs into the lower limb by passing under the inguinal ligament, and it innervates skin on the anterior and lateral surfaces of the thigh.

lateral pectoral nerve

A motor nerve originating in the lateral cord of the brachial plexus and composed of axons from C5–C7. It innervates the pectoralis major and pectoralis minor muscles.

lateral plantar nerve

A mixed nerve that is a terminal branch of the tibial nerve; it angles laterally from the medial plantar nerve along the sole of the foot.

Sensory

It innervates the skin on the lateral one-third of the sole and on the plantar side of the last 1 1/2 toes.

Motor

lesser occipital nerve

A sensory nerve composed of axons from spinal cord segments C2–C3. It innervates the skin over the back of the neck.

lingual nerve

A sensory branch of the mandibular trunk (CN V3). It is joined by the chorda tympani before entering the lateral floor of the mouth. The lingual nerve then runs toward the front of the mandible, between the hyoglossus and mylohyoid muscles, and ends near the front of the base of the tongue. It innervates the submandibular ganglion, the mucosa along the base of the mouth, the anterior two-thirds of the tongue, and the inner lower gingivae.

long thoracic nerve

A motor nerve composed of axons from spinal nerves C5–C7. It runs down along the lateral chest wall and innervates the serratus anterior muscle.

lumbar nerve

Any of the five pairs of spinal nerves originating in the lumbar segments of the spinal cord. Each lumbar spinal nerve emerges from the spinal canal through the intervertebral foramen below its corresponding vertebra. Lumbar spinal nerves innervate the lower limbs.

lumbar splanchnic nerve

Bundles of sympathetic axons from the lumbar ganglia of the sympathetic trunk that run to the inferior mesenteric and hypogastric plexuses.

major superficial petrosal nerve

mandibular nerve

Abbreviation: CN V3

1. The inferior trunk of the trigeminal cranial nerve. The mandibular nerve is both sensory and motor.

Sensory

The major sensory branches are the auriculotemporal, lingual, and inferior alveolar nerves, which innervate the lower teeth and gingivae and the skin of the lower lip, chin, and jaw up into the "sideburn area" in front of the ear.

Motor

The major motor branches are the lateral pterygoid, masseteric, deep temporal, and buccal nerves, which innervate the muscles of mastication (lateral and medial pterygoids, masseter, and temporalis).

Course

The mandibular nerve leaves the skull via the foramen ovale.

2. A motor branch of the facial nerve (CN VII) that innervates the facial muscles of the lower lip and chin.

masseteric nerve

A motor branch of the mandibular nerve (CN V3) that innervates the masseter muscle and the temporomandibular joint.

maxillary nerve

Abbreviation: CN V2

The middle trunk of the trigeminal cranial nerve. The maxillary nerve is purely sensory; its major branches are the pterygopalatine, posterior superior alveolar, zygomatic, and infraorbital nerves, which innervate the palate, nasal cavity, upper teeth, and the skin of the lower eyelids, checks, nose, and upper lip. COURSE: The maxillary nerve leaves the skull, and enters the pterygopalatine fossa, via the foramen rotundum.

medial antebrachial cutaneousnerve

A sensory nerve originating in the medial cord of the brachial plexus and composed of axons from spinal cord segments C8–T1, which innervates skin on the medial side of the forearm.

Synonym: medial cutaneous nerve of the forearm

medial brachial cutaneous nerve

A sensory nerve originating in the medial cord of the brachial plexus and composed of axons from spinal cord segments C8–T1. It innervates skin on the medial side of the arm.

Motor

median nerve

A mixed nerve of the upper limb originating in the lateral and medial cords of the brachial plexus and composed of axons from spinal cord segments C6–T1.

Sensory

It innervates the skin of the first 3 1/2 digits and the palm proximal to them.

Motor

In the forearm, it innervates the flexor carpi radialis, palmaris longus, pronator teres, flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus, and pronator quadratus. In the hand, it innervates the thenar muscles (other than the adductor pollicis and the deep head of the flexor pollicis brevis) and the lumbricals of digits 2 and 3.

Course

It runs in the anterior forearm, roughly midway between the radial and ulnar arteries; it becomes superficial near the wrist and then runs inside the carpal tunnel.

mental nerve

A sensory nerve, the terminal branch of the inferior alveolar nerve. It runs in the mandibular canal, emerges through the mental foramen, and innervates the mucosa of the lower lip and the skin of the lower lip and chin.

mixed nerve

A nerve containing both afferent (sensory) and efferent (motor) axons.

motor nerve

A nerve conveying efferent information to an effector target, such as a muscle or a gland.

myelinated nerve

mylohyoid nerve

A motor branch of the inferior alveolar nerve that arises just proximal to the mandibular foramen. It innervates the mylohyoid muscle and the anterior belly of the digastric muscle.

nasal nerve

Any of the medial, lateral, and external nasal nerves that are sensory branches of the nasociliary nerve. They enter the top of the nasal cavities and innervate the internal walls of the nose.

nasociliary nerve

A sensory branch of the ophthalmic nerve (CN V1). It passes over the top of the optic nerve in the orbit. Its branches include the anterior and posterior ethmoidal, medial, lateral, and external nasal, and infratrochlear nerves. It innervates the upper nasal cavity, the conjunctiva of the upper eyelid, and skin along the nose and upper eyelid.

nasopalatine nerve

A sensory and autonomic nerve that runs from the pterygopalatine ganglion through the adjacent sphenopalatine foramen into the roof of the posterior nasal cavity. Its branches innervate the roof, septum, and floor of the nasal cavity and, via the incisive canal, the hard palate and the gingivae behind the upper incisors.

ninth cranial nerve

noradrenergic nerve

A nerve that uses norepinephrine as its main neurotransmitter.

obturator nerve

A motor nerve originating in the lumbar plexus and composed of axons from spinal cord segments L2–L4. It passes into the thigh through the obturator foramen of the pelvic bones and innervates the adductor longus, adductor brevis, gracilis, pectineus, obturator externus, and adductor magnus muscles.

occipital nerve

oculomotor nerve

A somatic and visceral motor nerve originating in the midbrain oculomotor nucleus and the adjacent Edinger-Westphal nucleus. The oculomotor nerve runs in the subarachnoid space and cavernous sinus inside the skull and enters the orbit through the superior orbital fissure. Its somatic motor axons innervate the superior, medial, and inferior rectus muscles, the inferior oblique muscle, and the superior levator palpebrae muscle. Its preganglionic parasympathetic axons synapse in the ciliary ganglion; the ganglion cell axons (postganglionic parasympathetic axons) follow the short ciliary nerves into the eyeball to innervate the ciliary muscle of the lens of the eye and the pupillary constrictor muscles.

Synonym: third cranial nerve

RIGHT OLFACTORY NERVE

olfactory nerve

A sensory nerve with neuronal cell bodies located in the olfactory epithelium (a yellowish-brown thickened patch of epithelium found along the upper back walls of the nasal cavity). Axons from the receptor cells join into approximately 20 small nonmyelinated bundles (the olfactory nerves). These nerves pass into the skull through holes in the cribriform plate of the ethmoid bone and terminate in the ipsilateral olfactory bulb in spherical synaptic structures called glomeruli.

ophthalmic nerve

Abbreviation: CN V1

The superior trunk of the trigeminal cranial nerve. The ophthalmic nerve is purely sensory; its major branches are the nasociliary, frontal, and lacrimal nerves, which innervate the eyeball, upper part of the nasal cavity, and the skin of the upper eyelids, forehead, and front half of the scalp. COURSE: The ophthalmic nerve leaves the skull and enters the orbit through the superior orbital fissure.

optic nerve

A sensory nerve composed of the axons of the retinal ganglion cells in the eye. The nerve runs from the back of the eye, through the optic canal, and into the middle cranial fossa. In front of the stalk of the pituitary gland, the right and left optic nerves merge to form the optic chiasm. Here axons from the nasal portion of each retina cross to the other side and join the axons from the contralateral temporal retina to run as the optic tract, which synapses in the lateral geniculate bodies (nuclei) of the thalamus and the superior colliculus of the tectum of the midbrain. In the optic nerve, which runs from the eyeball to the optic chiasm, the full visual information from one eye is transmitted; in the optic tract, which runs from the optic chiasm to the thalamus and midbrain, the full visual information from one visual field is transmitted. Synonym: second cranial nerve

palatine nerve

Either of two nerves, the greater palatine nerve and the lesser palatine nerve, that leave the pterygopalatine ganglion and run down the greater palatine canal, giving rise to branches that innervate the nasal mucosa. At the bottom of the canal, the nerves branch to innervate the roof of the mouth, soft palate, and tonsil.

pancreatic nerve

Any of the autonomic nerves innervating the pancreas from the vagus nerve (CN X) and the splanchnic nerves (from spinal cord segments T5–T9).

parasympathetic nerve

A nerve composed of axons of the parasympathetic division of the autonomic nervous system. Parasympathetic innervation is always a chain of two consecutive axons. The first axon, the preganglionic parasympathetic axon, has its cell body in the brainstem or in the intermediate gray column of spinal cord segments S2–S4; the first axon leaves the brainstem through the oculomotor (CN III), facial (CN VII), glossopharyngeal (CN IX), or vagus (CN X) nerve, or it leaves the sacral spinal cord through a pelvic splanchnic nerve. The second axon in the chain, the postganglionic parasympathetic axon, has its cell body in a peripheral ganglion near its target tissue. The main transmitter used by both pre- and postganglionic parasympathetic axons is acetylcholine. In general, stimulation of parasympathetic nerves relaxes the body tone.

peripheral nerve

perivascular nerve

pharyngeal nerve

1. An autonomic nerve from the pterygopalatine ganglion that innervates the mucosa of the nasopharynx.

2. A sympathetic nerve from the superior cervical ganglia that innervates the pharynx and its surrounding pharyngeal plexus.

phrenic nerve

A mixed nerve composed of axons from spinal nerves C3 –C5. It descends through the neck behind the carotid sheath; in the chest, it lies between the mediastinal pleura and the pericardium. It is sensory and motor to the diaphragm and sensory to the pericardium.

pilomotor nerve

A motor nerve that innervates the arrectores pilorum muscles of hair follicles.

posterior antebrachial cutaneous nerve

A sensory branch of the radial nerve that innervates a strip of skin along the posterior surface (back) of the forearm.

Synonym: posterior cutaneous nerve of the forearm

posterior brachial cutaneous nerve

A sensory branch of the radial nerve that originates in the arm and that innervates a patch of skin along the posterior surface of the arm.

posterior cutaneous nerve of the arm

posterior cutaneous nerve of the forearm

posterior cutaneous nerve of the thigh

posterior femoral cutaneous nerve

A sensory nerve originating in the sacral plexus and composed of axons from spinal cord segments S1–S3. It innervates the skin of the lateral perineum, buttock, upper medial and posterior thigh, and calf.

Synonym: posterior cutaneous nerve of the thigh

presacral nerve

Superior hypogastric plexus.

nerve of the pterygoid canal

pressor nerve

pudendal nerve

A mixed nerve composed of axons from spinal nerves S2–S4. It follows the sciatic nerve out of the pelvis but immediately reenters through the lesser sciatic foramen. It innervates most of the structures of the perineum: it is sensory to the genitals and motor to the perineal muscles, the external urethral sphincter, and the external anal sphincter.

pulmonary nerve

Any of the sympathetic and parasympathetic nerves from the pulmonary plexus that innervate the bronchial muscles, glands, mucous membranes, and alveoli.

purinergic nerve

A nerve with axons that secrete adenosine triphosphate (ATP) or other purine nucleotides as a neurotransmitter or as a local chemical modulator.

radial nerve

A mixed nerve of the upper limb, the continuation of the posterior cord of the brachial plexus and composed of axons from spinal cord segments C5–T1.

Sensory

The radial nerve innervates skin along the lateral posterior arm via the posterior and lower lateral brachial cutaneous nerves. The radial nerve also innervates a strip of skin along the posterior forearm via the posterior antebrachial cutaneous nerve and the skin on the lateral half of the dorsal surface of the wrist, hand, and first 2 1/2 digits via the superficial branch of the radial nerve.

Course

From the posterior cord of the brachial plexus, the radial nerve runs with the deep brachial artery along the back of the humerus; it comes laterally around the humerus and continues distally, passing over the lateral condyle of the humerus. There it divides into the superficial and deep branches of the radial nerve, which continue into the forearm.

recurrent laryngealnerve

A branch of the vagus nerve (CN X). It leaves the vagus in the root of the neck: on the right, it loops under the subclavian artery, while on the left it loops under the arch of the aorta. It then ascends along the lateral wall of the trachea to the larynx where it innervates all the intrinsic muscles except the cricothyroid muscle; it is also sensory to the mucosa below the vocal folds. Injuries of the recurrent laryngeal nerve cause hoarseness, dysphagia, and dyspnea.

recurrent meningeal nerve

renal nerve

The lowest (least) splanchnic nerve, which carries sympathetic axons to the renal plexus.

sacral nerve

One of five pairs of dorsal or five pairs of ventral spinal nerves originating in the sacral segments of the spinal cord.

Sensory

The dorsal sacral spinal nerves innervate the skin and fascia over the sacrum and the medial gluteal region. The ventral sacral spinal nerves innervate the sacrospinous and sacrotuberous ligaments and the skin of the perineum.

Motor

sacral splanchnicnerve

A bundle of autonomic axons from the sympathetic trunk (ganglia S2–S3) that is en route to the inferior hypogastric plexus.

saphenous nerve

A sensory nerve that branches from the femoral nerve in the femoral triangle. It runs down the anterior and medial thigh and leg, accompanying the great saphenous vein, and it innervates the skin over the front and medial side of the knee, proximal leg, and medial side of the foot.

sciatic nerve

The largest nerve in the body. It originates in the sacral plexus and is composed of axons from spinal cord segments L4–S3. It runs along the back wall of the pelvis, exits through the greater sciatic foramen under the piriformis muscle, passes under the gluteus maximus muscle, and runs deeply along the posterior thigh. As it enters the popliteal fossa, its two internal components separate as the tibial and common peroneal nerves. The sciatic and its branches innervate the posterior thigh muscles (the flexors of the knee) and all the muscles, joints, and skin of the leg and foot.

second cranial nerve

secretory nerve

A nerve that behaves like an endocrine gland by secreting neurohormones into the blood stream. Secretory neurons are a characteristic of the hypothalamus, where they release vasopressin, oxytocin, somatostatin, corticotropin-releasing hormone, and thyrotropin-releasing hormone.

sensory nerve

A nerve that conveys afferent information, e.g., visual information from the eye or proprioceptive information from a joint.

seventh cranial nerve

sinuvertebral nerve

Any of the small sensory branches of the spinal nerves that join with axons from sympathetic ganglia to innervate the dura, local blood vessels, periosteum, and ligaments of the spinal canal at each vertebral level.

spinal accessory nerve

A motor nerve originating in the nucleus ambiguus in the medulla and in a column of motor neurons in the ventral horn of the upper cervical spinal cord. After exiting the skull through the jugular foramen, the nerve splits; its cranial trunk joins the vagus (CN X) and innervates striated muscles in the soft palate, pharynx, larynx, and esophagus; its spinal trunk continues down the neck to innervate the sternocleidomastoid and trapezius muscles.

spinal nerve

Any of the 31 sets of nerves originating in the spinal cord and emerging from the spinal canal through intervertebral foramina. Each spinal nerve is the concatenation of two sets of axons that emerge separately from the spinal cord: sensory axons (the dorsal root) and motor axons (the ventral root). See: illustration

illustration

splanchnic nerve

Any one of the paired, purely autonomic nerves from the thoracic sympathetic ganglia. The major splanchnic nerves are the greater, lesser, and least (smallest, renal) splanchnic nerves, which carry preganglionic sympathetic axons from ganglia 6–10 of the thoracic sympathetic trunk to the prevertebral ganglia (celiac, superior mesenteric, and aorticorenal ganglia) in the abdomen.

subcostal nerve

The ventral ramus of thoracic spinal nerve T12. It runs along the lower border of the twelfth rib and continues down through the abdominal muscles to reach the abdominal midline over the pubic symphysis. It innervates the skin and muscles in the area of the T12 dermatome.

suboccipital nerve

A motor nerve composed of axons from the dorsal ramus of spinal nerve C1. It leaves the spinal canal between the skull and the first cervical vertebra, and it innervates the four small muscles of the suboccipital triangle, deep in the back of the neck at the base of the skull.

subscapular nerve

Either of the upper and lower subscapular nerves from the shoulder nerves that originate in the posterior cord of the brachial plexus and are composed of axons from spinal cord segments C5–C6. They innervate the subscapularis and teres major muscles.

sudomotor nerve

A postganglionic sympathetic nerve that stimulates sweat glands.

superficial fibular nerve

superficial peroneal nerve

One of the two major branches of the common peroneal nerve formed as the latter winds around the proximal neck of the fibula. The superficial peroneal nerve runs along the lateral leg, innervating the skin along the anterior surface of the leg and the dorsal surface of the foot and the peroneus longus and brevis muscles.

Synonym: superficial fibular nerve

superior gluteal nerve

A nerve composed of axons from spinal nerves L4–S1. It follows the sciatic nerve out of the pelvis, and it innervates the gluteus medius, gluteus minimus, and tensor fasciae latae muscles.

supraorbital nerve

A sensory branch of the frontal nerve. It leaves the upper edge of the orbit through the supraorbital notch (or foramen) and divides into branches that innervate the conjunctiva lining the upper eyelid, the mucosa of the frontal sinus, and the skin of the upper eyelids, forehead, and front half of the scalp.

suprascapular nerve

A mixed shoulder nerve originating in the superior trunk of the brachial plexus and composed of axons from spinal cord segments C5–C6. It runs through the scapular notch under the superior transverse scapular ligament.

Sensory

It innervates the glenohumeral joint.

Motor

It innervates the supraspinatus and infraspinatus muscles.

supratrochlear nerve

A sensory branch of the frontal nerve. It leaves the upper edge of the orbit medial to the supraorbital nerve, and it innervates the skin of the middle of the forehead.

sural nerve

A sensory nerve composed of axons from the tibial and common fibular nerves in the posterior leg. It runs superficially along the posterior leg and lateral side of the foot and innervates the skin along its route.

sympathetic nerve

A nerve composed of axons of the sympathetic division of the autonomic nervous system. Sympathetic innervation is always a chain of two consecutive axons. The first axon, the preganglionic sympathetic axon, has its cell body in the intermediolateral column of spinal cord segments T1–L1; the first axon leaves the spinal cord through a ventral root and synapses in a peripheral sympathetic ganglion, either in the sympathetic trunk (the paraspinal ganglia) or in the prevertebral ganglia. The second axon in the chain, the postganglionic sympathetic axon, has its cell body in a peripheral ganglion, and it follows a splanchnic or other sympathetic nerve to its target tissue. The main transmitter used by preganglionic sympathetic axons is acetylcholine; for postganglionic sympathetic axons, it is norepinephrine. In general, stimulation of sympathetic nerves activates the body, putting it in "fight or flight" mode.

temporal nerve

1. Any of the two or three branches of the anterior division of the mandibular nerve (CN V3) that innervates the temporalis muscle. Synonym: deep temporal nerve

2. Any the branches of the facial nerve (CN VII) that run over the zygomatic arch to innervate facial muscles of the upper eyelid and forehead.

tenth cranial nerve

third cranial nerve

thoracic nerve

Any of the twelve pairs of spinal nerves originating in the thoracic segments of the spinal cord. Each thoracic nerve emerges from the spinal canal through the intervertebral foramen below its corresponding vertebra. Thoracic spinal nerves innervate the trunk.

thoracodorsal nerve

A nerve originating in the posterior cord of the brachial plexus and composed of axons from spinal cord segments C6–C8. It runs inside the posterior axillary wall and along the lateral edge of the back to innervate the latissimus dorsi muscle.

tibial nerve

The continuation of the sciatic nerve beyond the apex of the popliteal fossa after the common fibular nerve has branched off. The tibial nerve runs alongside the tibial artery in the posterior leg; for most of its course, it is beneath the gastrocnemius and soleus muscles. Along its route, the tibial nerve innervates the posterior muscles of the knee and leg, and it ends, under the flexor retinaculum at the heel of the foot, by branching to form the medial and lateral plantar nerves.

trigeminal nerve

A mixed nerve arising from the pons in a large sensory root and a smaller motor root.

Sensory

Somatic sensory fibers from the face collect into three major trunks: the ophthalmic, from the region of the eyes and above; the maxillary, from the region of the lower eyelids and cheeks down to the upper lip, teeth, and gingivae; and the mandibular, from a region that follows the sideburns down along the jaw and that includes the lower lips, teeth, and gingivae. Neuronal cell bodies for these fibers are located in the trigeminal (Gasserian, semilunar) ganglion along the floor of the middle cranial fossa; the axons of the ganglion cells synapse in the pons and medulla.

Motor

Somatic motor axons originate in motor nuclei in the pons and, running only in the mandibular trunk of the trigeminal nerve, innervate the muscles used in chewing.

Course

The trigeminal nerve emerges from the pons via a large sensory root and a small adjacent motor root; both run together to the trigeminal ganglion. From the ganglion, three trunks leave the cranial cavity separately: the ophthalmic trunk (ophthalmic nerve, CN V1) enters the back of the orbit through the superior orbital fissure, the maxillary trunk (maxillary nerve, CN V2) leaves through the foramen rotundum, and the mandibular trunk (mandibular nerve, CN V3) leaves through the foramen ovale.

Synonym: fifth cranial nerve

trochlear nerve

A somatic motor nerve originating in the trochlear nucleus in the midbrain. The nerve leaves the midbrain just behind the inferior colliculus; it crosses dorsally, and then runs in the subarachnoid space and the cavernous sinus until it enters the back of the orbit through superior orbital fissure. It innervates the superior oblique muscle.

twelfth cranial nerve

tympanic nerve

Any of the small nerves from the tympanic plexus, which lies along the lower medial wall of the tympanic cavity. They innervate the mucosa of the tympanic cavity, Eustachian tube, and mastoid air cells.

ulnar nerve

A mixed nerve of the upper limb originating in the medial cord of the brachial plexus and composed of axons from spinal cord segments C7–T1.

Sensory

It innervates the skin of the last 1 1/2 digits and the palm proximal to them.

Motor

In the forearm, it innervates the flexor digitorum profundus, abductor digiti minimi, flexor carpi ulnaris, and flexor digiti minimi. In the hand, it innervates most of the intrinsic muscles (the hypothenar, interosseous, adductor pollicis, deep head of the flexor pollicis brevis, opponens digiti minimi, and palmaris brevis muscles and the medial lumbricals of digits 4 and 5).

Course

It runs along the medial side of the anterior forearm. It becomes superficial near the wrist and passes into the hand above (superficial to) the flexor retinaculum.

unmyelinated nerve

, nonmyelinated nerve

Peripheral axons that are surrounded by Schwann cells but are not enwrapped by rolls of Schwann cell membrane; extensions of the Schwann cells isolate unmyelinated axons from each other. Unmyelinated axons are small in diameter and transmit signals more slowly than myelinated axons.

uterine nerve

Any of the autonomic nerves innervating the uterus. They emerge from the inferior hypogastric plexus and follow the uterine arteries; in the uterus, the axons distribute throughout the myometrium and endometrium.

vagus nerve

A nerve that arises from the medulla and has branches to many organs

Sensory

Visceral sensory fibers from the lower pharynx, larynx, thoracic organs, and abdominal viscera join proprioceptive sensory fibers from the muscles of the soft palate, pharynx, and larynx and sensory taste fibers from the root of the tongue and the epiglottis. These axons enter the vagus nerve along its length and run to the superior and inferior (nodosal) ganglia of the vagus nerve; these ganglia lie within and just below the jugular foramen of the skull. The axons of cell bodies in the ganglia then take the vagus nerve to their various synaptic sites in the medulla.

Motor

Somatic motor axons from hindbrain motor nuclei run in the vagus nerve and innervate the soft palate, pharynx, and larynx. Preganglionic parasympathetic axons from the dorsal motor nucleus of the vagus take the vagus nerve to provide most of the parasympathetic innervation of the body below the neck and above the pelvis, including the lungs, heart, and abdominal viscera.

Course

The vagus forms from a line of small rootlets along the lower medulla; the rootlets collect into a single nerve, which emerges from the skull through the jugular foramen, along with the glossopharyngeal (CN IX) and spinal accessory (CN XI) nerves. The vagus nerve continues caudally in the carotid sheath between the internal jugular vein and the carotid artery, giving off branches along the way. It then joins the esophageal plexus and continues along the esophagus as it passes through the diaphragm; in the abdomen, the vagus nerve splits into branches that innervate all the abdominal viscera.

Synonym: tenth cranial nerveillustration

vasoconstrictor nerve

A sympathetic nerve that stimulates the constriction of smooth muscle cells in arterial walls.

vasodilator nerve

A nerve conducting impulses that bring about dilation of a blood vessel.

vasomotor nerve

A nerve that controls the caliber of a blood vessel; a vasoconstrictor or vasodilator nerve.

vasosensory nerve

Any nerve providing sensory fibers for a vessel.

vestibular nerve

The component of the vestibulocochlear nerve (CN VIII) with axons carrying sensory information about equilibrium and spatial orientation; it connects the vestibular ganglion with the vestibular nuclei in the brainstem.

vestibulocochlear nerve

The eighth cranial nerve, a sensory nerve for hearing and equilibrium. Cell bodies of the vestibular neurons are located in the vestibular ganglion in the inner ear; their receptor terminals end in the saccule, utricle, and semicircular ducts. Cell bodies of the cochlear neurons are located in the spiral ganglion in the inner ear; their receptor terminals end in the spiral organ of Corti. Axons of the neuron cell bodies in the vestibular and spiral ganglia run to the CNS side-by-side in the petrous process of the temporal bone; they exit through the internal acoustic meatus and enter the brainstem at the junction of the pons and the medulla.

See: illustration

vidian nerve

A short efferent nerve formed from the merger of the deep petrosal and greater petrosal nerves. The vidian nerve carries postganglionic sympathetic axons from the superior cervical ganglion and preganglionic parasympathetic axons from the superior salivatory nucleus (in the pons); it also carries taste axons from the palate. The vidian nerve exits the skull through the pterygoid (vidian) canal and connects to the pterygopalatine ganglion inside pterygopalatine fossa.

Synonym: nerve of the pterygoid canal

visceral nerve

A peripheral nerve that contains axons of the autonomic nervous system, either transmitting afferent signals from mucous membranes, glands, and vessels (visceral sensory nerves) or transmitting efferent signals to smooth muscles and glands (visceral motor nerves). Visceral motor nerves always synapse in a ganglion between their origin in the central nervous system and their termination in a muscle or gland.

zygomatic nerve

1. A sensory branch of the maxillary nerve (CN V2). It divides into the zygomaticofacial and zygomaticotemporal nerves along the floor of the orbit; these nerves innervate the skin of the cheeks.

2. Any of the motor branches of the facial nerve (CN VII) that run roughly horizontally through the cheek and innervate the facial muscles between the mouth and the lower eyelid.

nerve

A pinkish-white, cord-like structure consisting of bundles of long fibres (AXONS) of nerve cells and fine blood vessels held together by a connective tissue sheath. Individual fibres are usually insulated with a layer of white fatty material called myelin. The larger nerves contain both MOTOR and SENSORY fibres. Twelve pairs of nerves arise directly from the brain. These are called cranial nerves and carry impulses subserving smell, eye movement, vision, facial movement and sensation, all other sensation in the head, hearing, taste, movements of the soft palate, tongue and neck muscles, and control of the heartbeat and the secretion of stomach acid. 31 pairs of nerves emerge from the spinal cord. These control all the other muscles of the body and carry impulses for sensation from all parts of the body to the spinal cord and thence to the brain.

nerve

(in animals) a bundle of nerve fibres, usually containing both afferent neurons (to the CENTRAL NERVOUS SYSTEM), and efferent neurones (away from CNS), together with associated connective tissue and blood vessels, situated in a common sheath of CONNECTIVE TISSUE and lying outside the CNS.

Nerve

Fibers that carry sensory information, movement stimuli, or both from the brain and spinal cord to other parts of the body and back again. Some nerves, including the vagus nerve, innervate distantly separated parts of the body.

spinal nerve one of 31 pairs of nerves, originating from each somatic division (segment of the spinal cord); each pair is named from the area of the vertebral column from which they exit (cervical [C1-7]; thoracic [T1-12]; lumbar [L1-5]; sacral [S1-7]); each is linked to the spinal cord by a ventral (anterior) root (motor fibres of lower motor neurone), and a dorsal (posterior) root (sensory fibres of the first sensory neurone [whose dorsal root contains dorsal root ganglion, made up of cell bodies of first sensory neurone])

Awareness of the weight of the tip of a sterile hypodermic needle on a 2-mL syringe, filled with water, on the skinOr awareness of the pressure exerted by the metal end of a NeurotipOr awareness of the pressure applied to the skin by an algometer

Blunt/sharp

Neurotip (plastic end) + Neurotip (metal end)

Temperature

Free, fine nerve endings of C nerve fibres

Awareness of the contact of cold or heat (e.g. tubes of hot or cold water)

Vibration

Pacinian corpuscles at the termini of A-beta nerve fibres

Awareness of vibration when the instrument is placed against a bony prominence, using:1. a 128-Hz (middle C) tuning fork (which is appreciated as present or absent)2. a Rykel-Seiffer 128-Hz tuning fork (the tips of which are weighted and indicate the degree of perceived vibration, in arbitrary units, so that the level of sensory awareness can be recorded; normal sensation = >4)3. Neuraethesiometer; normal sensation = appreciation of > 23V vibratory stimulus

Proprioception

The examiner moves a joint and the patient identifies the direction of movement

Protective pain

Free, fine nerve endings of A-delta and C fibres

10G monofilament (also known as the 5.07 Semmes-Weinstein monofilament)The normal patient will be able to detect the contact of the tip of the nylon monofilament across the majority of the plantar surface

Ankle jerk test, where sudden stretch of the muscle unit, from the contact of the tendon hammer at the tendo Achilles approximately 5cm proximal to its insertion at the calcaneum, excites afferent nerve endings which link within the spinal cord to efferent nerves that pass to the gastrocnemius muscle and cause a brief muscle contraction or twitch

Patients may be unaware of their loss of some or all distal sensation; sensory loss may present as degrees of numbness, paraesthesia or hyperalgesia. The patient should lie relaxed on a couch throughout the assessment, and not watch the tests, in order to avoid visual prompts. Sensory evaluation should be carried out in a systematic manner, with all areas of the foot and all sensory modalities assessed. The distribution of altered sensation (e.g. dermatomal loss; distal loss) is noted on an appropriate form retained within the patient's case notes. Where possible the same clinician should carry out any repeat tests, and repeat tests, e.g. every 6-12 months should be made at the same time of day as the original assessment, due to the diurnal variation in sensory awareness.

nerve

A whitish cord made up of myelinated or unmyelinated nerve fibres held together by connective tissue sheath in bundles and through which stimuli are transmitted from the central nervous system to the periphery or vice versa.abducens nerve Sixth cranial nerve. It has its origin from the abducens nucleus at the lower border of the pons and at the lateral part of the pyramid of the medulla. It passes through the cavernous sinus and enters the orbit through the superior orbital fissure. It supplies motor innervation to the ipsilateral lateral rectus muscle. Additionally, interneurons leave the abducens nucleus and project to the contralateral medial rectus sub nucleus to allow conjugate gaze. A lesion in the nuclear region will cause gaze palsy, whereas an abducens nerve lesion will produce only an abduction deficit. Seeabducens nucleus; paralysis of the sixth nerve.cranial nerve's Twelve pairs of nerves, one set on each side of the brain, that emerge, or enter the cranium. They carry sensory information from the sense organs, the muscles of the head, neck, shoulders, heart, viscera and vocal tract. The motor neurons with axons in the cranial nerves control pupil diameter, accommodation, movements of the eyes and eyelids, mastication, facial expression, head movements, as well as cardiorespiratory and digestive functions.nerve fibre layerSeeretina.fifth cranial nerveSeetrigeminal nerve.fourth cranial nerveSeetrochlear nerve.frontal nerveSeeophthalmic nerve.nerve impulseSeeaction potential.infratrochlear nerveSeeophthalmic nerve.lacrimal nerveSeeophthalmic nerve.long ciliary nerve One of a pair of nerves that comes off the nasociliary nerve and runs with the short ciliaries, pierces the sclera, travels in the suprachoroidal space and supplies sensory fibres to the iris, cornea, and ciliary muscle and sympathetic motor fibres to the dilator pupillae muscle (Fig. N2). Seeophthalmic nerve; pupil light reflex.nasociliary nerveSeeophthalmic nerve.oculomotor nerve Third cranial nerve. It is classified as a motor nerve. Its origin lies in the tegmentum of the midbrain. It passes through the cavernous sinus and just before it enters the orbit it divides into a small superior and a larger inferior division. Both divisions penetrate into the orbit through the superior orbital fissure. In the orbit the superior division passes inward above the optic nerve to supply the superior rectus and the levator palpebrae superioris muscles. The inferior division sends branches to the medial rectus, the inferior rectus and inferior oblique muscles, as well as providing parasympathetic fibres to the sphincter pupillae and ciliary muscles via a branch to the ciliary ganglion. Seeoculomotor nucleus; paralysis of the third nerve.ophthalmic nerve This is the smallest of the three divisions of the trigeminal nerve, the other two being the maxillary and mandibular branches. It comes off the medial and upper part of the convex anterior border of the gasserian ganglion (trigeminal ganglion), passes through the cavernous sinus and just behind the superior orbital fissure it divides into three branches, the lacrimal, frontal and nasociliary, which pass through the fissure to enter the orbit. (1) The smallest of the three, the lacrimal nerve, supplies sensory fibres to the lacrimal gland, the skin of the upper eyelid and the conjunctiva. Just before reaching the gland the nerve communicates with the zygomaticotemporal nerve (itself a branch of the zygomatic nerve). This branch contains parasympathetic fibres from the facial nerve that pass to the lacrimal gland. (2) The frontal nerve, which is the largest of the three divisions, divides into the supratrochlear and supraorbital nerves. The supratrochlear further anastomoses with the infratrochlear nerve and supplies the lower part of the forehead, the upper eyelid and the conjunctiva. The infratrochlear supplies sensory fibres to the skin and conjunctiva round the inner angle of the eye, the root of the nose, the lacrimal sac and canaliculi and caruncle. The supraorbital nerve sends sensory fibres to the forehead, the upper eyelid and conjunctiva. (3) The nasociliary nerve gives origin to several nerves: the long ciliary nerves, the long or sensory root (ramus communicans) to the ciliary ganglion, the posterior ethmoidal nerve and the infratrochlear nerve (Fig. N2).optic nerve Second cranial nerve. It forms a link in the visual pathway. It takes its origin at the retina and is made up of nearly 1.2 million fibres from the ganglion cells and some efferent fibres that end in the retina. The nerve runs backward from the eyeball and emerges from the orbit through the optic canal and then forms the optic chiasma. The total length of the optic nerve is 5 cm; the portion before the chiasma called intracranial being about 1 cm, the intracanalicular 6 mm, the intraorbital 3 cm and the intraocular 0.7 mm. The optic nerve is more often divided into only two portions: the intraocular (bulbar) portion and the orbital (retrobulbar) portion (Fig. N2). Seeoptic atrophy; pupillary fibres; optic neuritis; anterior ischaemic optic neuropathy; papilloedema.short ciliary nerve One of six to ten branches from the ciliary ganglion that enters the eye around the optic nerve, travels in the suprachoroidal space and innervates the ciliary muscle, the sphincter pupillae muscle and the cornea. Seepupil light reflex.sixth cranial nerveSeeabducens nerve.supraorbital nerve; supratrochlear nerveSeeophthalmic nerve.third cranial nerveSeeoculomotor nerve.trigeminal nerve Fifth cranial nerve. It is the largest of the cranial nerves. It originates above the middle of the lateral surface of the pons as two divisions, a larger sensory root and a motor root. The sensory root passes to the gasserian ganglion (trigeminal ganglion) and from that ganglion the three divisions of the fifth nerve are given off: the ophthalmic, maxillary and mandibular nerves. The fifth nerve is sensory to the face, the eyeball, the conjunctiva, the eyebrow, the teeth, the mucous membranes in the mouth and nose. The motor root of the nerve has no connection with the ganglion. It joins the mandibular nerve and is motor to the muscles of mastication.trochlear nerve Fourth cranial nerve. It is the most slender of the cranial nerves but with the longest intracranial course (75 mm). It is the only motor nerve that originates from the dorsal surface of the brain between the midbrain and the cerebellum. It passes through the cavernous sinus and then enters the orbit through the superior orbital fissure and supplies motor fibres to the superior oblique muscle. Seetrochlear nucleus; paralysis of the fourth nerve.zygomatic nerve A branch of the maxillary division of the trigeminal nerve, it enters the orbit by the inferior orbital fissure and soon divides into the zygomaticotemporal and zygomaticofacial branches. The former gives a twig to the lacrimal nerve and is thought to conduct autonomic fibres to the lacrimal gland and the latter supplies the skin over the zygomatic bone.

Fig. N2 Diagram of the ophthalmic division of the trigeminal nerve (fifth). This is a view of the right eye from above (c.b.z, communicating branch to the zygomatic nerve)

nerve

(nĕrv) [TA]

A whitish cordlike structure composed of one or more bundles (fascicles) of myelinated or unmyelinated nerve fibers, or more often mixtures of both, coursing outside the central nervous system, together with connective tissue within the fascicle and around the neurolemma of individual nerve fibers (endoneurium), around each fascicle (perineurium), and around the entire nerve and its nourishing blood vessels (epineurium).

[L. nervus]

nerve,

n a cordlike structure that conveys impulses between a part of the central nervous system and some part of the body and consists of an outer connective tissue sheath and bundles of nerve fibers. See also each of the individual nerves of the head and neck as they are listed.

nerve, abducent (VI),

n the sixth cranial nerve; a small, completely motor nerve arising in the pons, supplying the lateral rectus muscle of the eye.

nerve, accessory,

n See nerve, spinal accessory.

nerve, acoustic (VIII),

n the eighth cranial nerve; the vestibulocochlear nerve; a sensory nerve consisting of a vestibular portion and an auditory (or cochlear) portion.

nerve(s), afferent, in pulp,

n any nerve that originates as a terminal free nerve ending in the dental pulp tissue and travels to the second and third divisions (maxillary nerve and mandibular nerve) of the cranial trigeminal nerve (cranial nerve V).

nerve, alveolar,

n afferent nerves that convey impulses from the pulp tissue and periodontium of the maxillary teeth to the maxillary division of the cranial trigeminal nerve.

nerve, anterior superior alveolar,

n alveolar nerve that conveys impulses from the pulp tissue and periodontium of the maxillary anterior teeth to the infraorbital nerve.

nerve, auriculotemporal

n a nerve that transmits feeling from the external ear, scalp, and parotid salivary gland to the mandibular division of the cranial trigeminal nerve.

nerve, branchial,

n one of five cranial nerves that supply the derivatives of the branchial arches: trigeminal (V), facial (VII), glossopharyngeal (IX), vagus (X), and spinal accessory (XI). Each branchial nerve may have a variety of functions, including visceral motor and visceral and somatic sensory functions.

nerve, buccal (long),

n afferent nerve that conveys impulses from the facial periodontium of the mandibular molars and gingiva to the mandibular division of the cranial trigeminal nerve.

nerve, chiasma, optic,

n the decussation, or crossing, of optic nerve fibers from the medial side of the retina on one side to the opposite side of the brain.

nerve, chorda tympani

n a parasympathetic and special sensory branch of the facial nerve supplying the submandibular and sublingual glands and the anterior two thirds of the tongue (taste).

nerve, cochlear

n one of the two major branches of the eighth cranial nerve; a special sensory nerve for the sense of hearing that transmits impulses from the organ of Corti to the brain.

nerve, cranial,

n any one of 12 paired nerves, classified in three sets, arising directly in the brain and supplying various tissues of the head and neck. The cranial nerves are the special somatic sensory nerves: olfactory (I), optic (II), and vestibulocochlear (acoustic) (VIII); the somatic motor nerves: oculomotor (III), trochlear (IV), abducent (VI), and hypoglossal (XII); and the branchial nerves: trigeminal (V), facial (VII), glossopharyngeal (IX), vagus (X), and spinal accessory (XI).

nerve, deep temporal,

n an anterior and a posterior nerve that branch away from the mandibular nerve of the trigeminal nerve and extend deep into the temporalis muscle, which is used during mastication.

nerve degeneration,

n the reversion to a less organized and functioning state, usually detected by the loss of ability to conduct or transmit nerve impulses. Advanced degeneration might show cellular decomposition.

nerve ending,

n the terminal of a nerve fiber, usually in synapse with another fiber or in a sensory organ.

nerve, facial (VII),

n the seventh cranial nerve; a mixed nerve supplying motor fibers to the facial muscles, the stapedius, and posterior body of the digastric; sensory fibers from the taste buds in the anterior two thirds of the tongue (via the chorda tympani); and general visceral autonomic fibers for the submandibular and sublingual salivary glands. It travels unilaterally over the face and at one point is located in the parotid salivary gland, which it does not serve. However, pain in the parotid gland indicates a glandular malignancy, and complications with an inferior nerve block can also result from its location there.

The cranial nerves.

nerve fiber,

n a slender process of a neuron, usually the axon. Each fiber is classified as myelinated or unmyelinated.

nerve, frontal,

n afferent nerve from the union of the superorbital and supratrochlear nerves that carries information from the forehead, scalp, nose, and upper eyelids to the ophthalmic division of the cranial trigeminal nerve.

nerve, glossopharyngeal (IX)

n the ninth cranial nerve; a mixed motor and sensory nerve arising in the medulla and supplying motor efferents to stylopharyngeal muscles and other pharyngeal muscles; visceral motor efferents via the otic ganglion for the parotid gland; special visceral afferents from the taste buds in the posterior third of the tongue; and general sensory afferents from the pharynx and posterior aspects of the oral cavity. It is essential to the sense of taste.

nerve, greater (anterior) palatine,

n the nerve originating in the pterygopalatine ganglion that supplies the hard palate, part of the soft palate, and its associated lingual mucosa.

nerve, greater petrosal

n one of the two nerves that branch off of the facial nerve and help control the muscles used in facial expression; this nerve also carries impulses to the lacrimal gland and the nasal cavity, and to and from the palate. The nerve has both afferent and efferent fibers.

nerve, hypoglossal (XII),

n the twelfth cranial nerve; a motor nerve that arises in the medulla and supplies extrinsic and intrinsic muscles of the tongue. Each nerve has four major branches, communicates with the vagus nerve, and connects to the nucleus XII in the brain.

nerve, incisive,

n afferent nerve that merges with the mental nerve to later create the inferior alveolar nerve in the mandibular canal. This nerve transmits feeling from the pulp tissue and facial periodontium of the mandibular anterior teeth and premolars to the mandibular division of the cranial trigeminal nerve.

nerve, inferior alveolar,

n a motor and general sensory branch of the mandibular nerve, with mylohyoid, inferior dental, mental, and inferior gingival branches.

nerve, infraorbital,

n afferent nerve that enters through the infraorbital foramen and canal to merge with the maxillary branch of the cranial trigeminal nerve.

nerve, intermediate,

n the parasympathetic and special sensory division of the facial nerve with chorda tympani and greater petrosal branches.

nerve, lacrimal,

n afferent nerve that is part of the ophthalmic division of the cranial trigeminal nerve and controls secretions in the upper eyelid, lacrimal gland, and the conjunctiva.

nerve, lingual,

n a general sensory branch of the mandibular nerve having sublingual and lingual branches and connections with the hypoglossal nerve and chorda tympani.

n a nerve that branches off the inferior alveolar nerve, emerging from the mandible through the mental foramen and branching further to provide sensory innervation to the tissues of the chin and lower lip and the labial mucosa of the mandibular premolars and anterior teeth.

nerve, middle superior alveolar,

n alveolar nerve that conveys impulses from the pulp tissue and periodontium of the gingiva and the maxillary premolar teeth to the infraorbital nerve. This nerve is not always present in all persons. If not present, the premolars are innervated by the posterior superior alveolar nerve.

nerve, mylohyoid,

n a branch of the mandibular division of the cranial trigeminal nerve that serves the mylohyoid and digastric muscles of the oral cavity. It is thought to be a possible alternative innervation for the pulp tissues of the mandibular first molar in some cases.

nerve, nasociliary

n one of three branches of the cranial trigeminal nerve that controls parts of the eyes, nasal cavity, and paranasal sinuses.

nerve, nasopalatine

n afferent nerve that conveys impulses from the lingual periodontium of the maxillary anterior teeth bilaterally and the anterior hard palate to the maxillary division of the cranial trigeminal nerve.

nerve, oculomotor (III)

n the third cranial nerve; primarily a motor nerve arising from the midbrain and supplying motor efferents to the superior rectus, medial rectus, inferior rectus, and inferior oblique eye muscles, as well as autonomic fibers via the ciliary ganglion to the ciliary body and the iris.

nerve, olfactory (I)

n the first cranial nerve; a special sensory nerve for the sense of smell.

nerve, ophthalmic

n the ophthalmic division of the trigeminal nerve, arising in the trigeminal ganglion and supplying general sensory fibers via the frontal, lacrimal, and nasociliary branches.

nerve, optic (II),

n the second cranial nerve; a special sensory nerve for vision. It consists mainly of coarse, myelinated fibers that arise in the retinal ganglionic layer of the eye, traverse the thalamus, and connect with the visual cortex of the brain.

nerve, palatine,

n the two afferent nerves of the maxillary division of the cranial trigeminal nerve. The greater palatine nerve innervates the posterior hard palate and lingual periodontium of the maxillary molar teeth, while the lesser palatine nerve innervates the soft palate and palatine tonsillar tissue.

nerve, posterior superior alveolar,

n alveolar nerve that conveys impulses from the maxillary sinus, gingiva, pulp tissue, and periodontium of the maxillary molar teeth to the infraorbital nerve or to the maxillary nerve directly.

nerve regeneration,

n the reconstruction and renewal of cell structure and function; generally restricted to myelinated nerve fibers.

nerve repositioning,

n the surgical redirecting of the inferior alveolar and/or mental nerve to allow longer implants to be placed in a mandible that has extensive deterioration of the posterior ridge. Some temporary or long-term loss of sensation to the lip, tongue, chin and/or gingival tissue may result. Also known as nerve lateralization and nerve transpositioning.

nerve(s), somatic motor,

n (cranial), the somatic motor nerves–oculomotor (III), trochlear (IV), abducent (VI), and hypoglossal (XII)–largely comparable to the ventral motor roots of the spinal nerves. They are composed almost entirely of somatic motor fibers that emerge ventrally from the brainstem. Their arrangement is closely correlated with the distribution of the myotomes in the head. The oculomotor, trochlear, and abducent nerves, which supply the eye musculature, have the same myotomic origin and arrangement as the somatic muscles of the trunk and extremities.

nerve(s), special somatic sensory,

n the structural arrangements from typical sensory nerves by which the three main sense organs, nose, eyes, and ears, are innervated. The sensory nerves are the olfactory (I), optic (II), and vestibulocochlear (acoustic) nerves (VIII).

n the eleventh cranial nerve; a motor nerve that derives its origin in part from the medulla and in part from the cervical spinal cord. Its internal ramus joins with the vagus nerve to supply some of the muscles of the larynx. Its external ramus joins with the spinal nerves to supply the sternocleidomastoid and trapezius muscles. The nerve and its relationship to head posture is important in maintaining stable occlusal relationships of vertical dimension and centric relation.

nerve, tensor tympani,

n a small motor branch of the mandibular nerve.

nerve, trigeminal (V)

n the fifth cranial nerve; a mixed motor and sensory nerve connected with the pons through three roots (motor, proprioceptive, and large sensory), the latter root expanding into the trigeminal ganglion, from which arise the ophthalmic, masseteric, and mandibular divisions. It serves the muscles of mastication and cranial muscles through its motor root and serves the teeth, tongue, and oral cavity and most of the facial skin through its sensory root.

nerve, trochlear (IV)

n the fourth cranial nerve; a small motor nerve arising ventrally in the midbrain and supplying the inferior oblique muscle of the eye.

nerve trunk,

n a particularly sizeable bundle of axons or nerve fibers.

nerve, vagus (X)

n the tenth cranial nerve; a mixed parasympathetic, visceral, afferent, motor, and general sensory nerve with laryngeal, pharyngeal, bronchial, esophageal, gastric, and many other branches.

nerve, vestibular (VIII),

n one of the two major branches of the eighth cranial nerve; a special sensory nerve for the sense of balance and the transmission of space-orientation impulses from the semicircular canals to the brain.

nerve, vestibulocochlear (VII),

n the seventh cranial nerve; acoustic nerve; a sensory nerve consisting of a vestibular portion and an auditory, or cochlear, portion.

nerve, zygomatic

n the afferent nerve of the maxillary division of the cranial trigeminal nerve that serves the skin of the cheek and temple. It also innervates the lacrimal gland.

nerve(s), dentinal,

n any of the afferent or sensory neurons associated with the odontoblastic processes in the dentinal tubules and the attached cell body of the odontoblasts within the pulp tissue. These nerves may allow for an awareness of pain due to their monitoring of environmenal changes within the dentin. There is some controversy about their overall location in the dentin tubule (full length, partial, or not at all).

nerves, efferent,

n motor nerves that carry impulses from the brain or spinal cord toward the periphery of the body to activate muscles, usually in response to impulses received from sensory nerves.

nerve(s), periodontal ligament,

n the sympathetic fibers of the autonomic nervous system with enclosed nerve endings that control blood flow within the vessels and register pressure changes. Sensory or afferent fibers with free nerve endings cause an awareness of pain.

nerve(s), pulp,

n the sympathetic fibers of the autonomic nervous system located within the tissue that control blood flow within the vessels. Sensory or afferent fibers with free nerve endings in close proximity to the odontoblasts may cause an awareness of pain.

nerve

a macroscopic cordlike structure of the body, comprising a collection of nerve fibers that convey impulses between a part of the central nervous system and some other body region. For a complete list of the named nerves of the body, see Table 14.

Depending on their function, nerves are known as sensory, motor or mixed. Sensory nerves, or afferent nerves, carry information from the periphery of the body to the brain and spinal cord. Sensations of heat, cold, pressure and pain are conveyed by the sensory nerves. Motor nerves, or efferent nerves, transmit impulses from the brain and spinal cord to the periphery, especially the muscles. Mixed nerves are composed of both motor and sensory fibers, and transmit messages in both directions.

Together, the nerves make up the peripheral nervous system, as distinguished from the central nervous system, which consists of the brain and spinal cord. There are 12 pairs of cranial nerves, which carry messages to and from the brain. Spinal nerves arise from the spinal cord and pass out between the vertebrae. The various nerve fibers and cells that make up the autonomic nervous system innervate the glands, heart, blood vessels and involuntary muscles of the internal organs. For a complete list of nerves, see Table 14.

specimens taken from representative nerves by separation and removal of fascicles may provide useful information in the investigation of neuromuscular disorders or neuropathies. Consideration must be given to any resulting motor or sensory deficits that might result from the procedure. In dogs, the common peroneal, ulnar and tibial nerves are the usual sources.

nerve cuff

device used in the surgical repair of nerves to protect the site of anastomosis from an in-growth of connective tissue and to promote linear regeneration of neural elements.

depressor nerve

1. an inhibitory nerve whose stimulation depresses a motor center.

2. a nerve that lessens activity of an organ.

dermal nerve network

the organization of sensory nerve fibers to the dorsal root ganglia found in the dermis.

one that transmits impulses resulting in an increase in functional activity.

excitoreflex nerve

a visceral nerve that produces reflex action.

nerve fiber

a process of a neuron, especially the long slender axon which conducts nerve impulses away from the cell. It may be medullated or nonmedullated.

free nerve endings

see nerve endings (above).

fusimotor n's

those that innervate the intrafusal fibers of the muscle spindle.

gangliated nerve

any nerve of the sympathetic nervous system. Called also ganglionated.

nerve gas

organophosphorus compounds specially selected for their toxicity to humans and used in chemical warfare.

nerve growth factor

a protein dimer composed of two identical polypeptide chains secreted by nerve cells and necessary for the growth and survival of certain classes of nerve cells during development.

nerve impulses

the physicochemical change in a nerve fiber's membrane which is caused by stimulation, e.g. from a stretch receptor, and which transmits a record of the sensation, or, in another case, of a motor instruction to an effector organ.

inhibitory nerve

one that transmits impulses resulting in a decrease in functional activity.

medullated nerve

myelinated nerve.

modified free nerve endings

see nerve endings (above).

myelinated nerve

one whose axons are encased in a myelin sheath.

pelvic n's

nerves of the parasympathetic outflow. See Table 14.

peripheral nerve

any nerve outside the central nervous system. Injury to a nerve causes pain initially and if tissue is destroyed, loss of function follows; signs are weakness or paralysis, atrophy, lower temperature and depressed reflexes.

motor neurons originating in ventral gray columns of the spinal cord and certain parts of the brain and are connected to striated muscles derived from embryonic somites.

spinal nerve

a segmental nerve which consists of afferent and efferent axons from its dorsal and ventral roots.

splanchnic n's

those of the blood vessels and viscera, especially the visceral branches of the thoracic, lumbar and pelvic parts of the sympathetic trunks.

nerve stimulator

an electrical device used to deliver a short stimulus to a peripheral nerve as a test of its function. It can be used to assess the effects of a neuromuscular blocking agent during clinical anesthesia.

one concerned in controlling the caliber of vessels, whether as a vasoconstrictor or vasodilator.

vasosensory nerve

any nerve supplying sensory fibers to the vessels.

visceral afferent n's

nerves with cell bodies in spinal and cranial ganglia and which provide sensory innervation to thoracic and abdominal tissues.

visceral efferent n's

the parasympathetic component of the autonomic nervous system.

Patient discussion about nerve

Q. why does ADHD make kind of an hype to children? is it a nerve defect?

A. it's a complex interaction among genetic and environmental factors causing a disorder in the central nervous system. a study showed a delay in development of certain brain structures n the frontal cortex and temporal lobe, which are believed to be responsible for the ability to control and focus thinking.

Q. What is ERD examination?My doctor want to find where is nerve is sprained. How this examonation will help? If the nerve is sprained by muscles or vertebrae what treat may be given by a doctor?

A. Sorry, but never heard of an examination called ERD, especially not for sprained muscle. Do you mean ERS?

Anyway, you may read more here:www.nlm.nih.gov/medlineplus/sprainsandstrains.html

Q. Nerves of pregnant woman can cause damage to the fetus?

A. Well, if by nerves you mean nervousness or stress, it hasn't been proven that stress during pregnancy can cause damage to the fetus. However, stress can damage the woman's health by lowering the body immunity and making it harder for the body to fight inflammation, infections, etc.

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